The pressure that the legs have to endure can be stronger then the veins and the blood begin to slow 
down or get backed up. Strolling could be performed at any type of speed, to 
clear calories, and handled indoors on a treadmill, or outdoors on city roads,
neighborhood parks, or walkways. Biking can be carried out outdoors, in parks or 
along active streets, or in a health club in an enclosed environment.